Studies proposed for this project year continue in the major directions of the original research plan: 1. Induction of adaptive protection against shock by stimulation of reticuloendothelial system (RES). 2. Pharmacologic manipulation of the terminal vascular bed in- vivo to correct low flow. 3. Comparative pharmacology of vascular smooth muscle as related to structure-activity of vasotropic agents. Experimental techniques, shock models and classes of vasotropic materials used are essentially as previously reported. Specific groups of experiments planned will: a) measure RES function in animals subjected to stressful situations. b) Continue to explore RES stimulating materials compatible for man to correlate phagocytic indices with survival after experimental shock. c) Continue in-vivo studies of analogues and derivatives of vasoactive neurohypophyseal peptides to correlate their selective out-of-profile microvascular actions with survival after experimental shock. d) Continue developing more discriminating correlation of structure-activity of vasoactive drugs toward design of agents for shock therapy based on both in-vivo microcirculatory and in-vitro vascular smooth muscle studies. e) To reconcile in isolated mammalian (including man) blood vessels, the variable effects of vasoactive drugs in various vascular beds on the basis of their molecular structure.